Compound bearing systems for disc drives are known, for example, from U.S. Pat. No. 5,761,006 Sri-Jayantha et al. Systems are assembled from separate conventional components that are joined together to make an assembled compound bearing system. Typically, a conventional ball bearing is assembled within a flex bearing assembly and then a voice coil and a read/write head are assembled on the flex bearing. Such a compound bearing system includes a relatively large number of joints where the various bearing components are assembled with each other. Assembling and joining the components of such a bearing system by conventional methods inevitably leads to variability in the dynamic mechanical properties of the assembled bearings. Resonant mechanical frequencies and mechanical damping coefficients of the bearing system tend to have an undesired statistical spread in production and may, in some cases, require expensive hand trimming to assure uniform performance needed for mass production. Non-uniformity in thicknesses or assembly can twist the bearing system transverse to the plane of rotation, degrading performance of the disc drive.
Much smaller disc drive dimensions are becoming available in milli- and micro-disc drives, and the conventional assembled disc drive compound bearing system limits drive performance and becomes costlier and less practical to produce for use with these smaller disc drives.
A disc drive with a bearing and a method of fabricating a disc drive bearing which combine both flexible bearing and sliding bearing elements with increased uniformity is needed for mass production applications in smaller, miniaturized disc drives.
A disc drive comprises a base including an axle shaft. A disc stack is rotationally mounted to the base. A head assembly couples to the disc stack. The disc drive further includes a voice coil mounted to a bearing for positioning the head assembly. The bearing has an inner hub rotationally mounted on the axle shaft. The bearing has an outer hub having the voice coil and the head assembly mounted thereon. The outer hub is rotationally mounted to the inner hub through a plurality of flexible spokes that are integrally formed with the inner and outer hubs.
The bearing is formed by the method of etching from a substrate to provide an integrally formed inner hub, outer hub and spokes. The voice coil is deposited on the integrally formed assembly. The integral bearing is free of joints between the spokes and the inner and outer hubs. The bearings integrally formed by this method have uniform mechanical characteristics desired for miniature disc drives. The bearings can be mass produced by batch fabrication techniques.